1. Field of the Invention
The present invention relates to an inductance element and a method of manufacturing the same. More specifically, it relates to an inductance element which comprises a coil formed by winding a conductor directly on a substrate and a method of manufacturing the same.
2. Description of the Prior Art
In recent years, electronic circuits have been subjected to hybrid integration with improvement of chip elements. A hybrid integrated circuit includes a semiconductor integrated circuit and its external components such as a capacitor, a resistor and a coil packaged in a unit, thereby to remarkably reduce the number of components of electronic equipment and simplify assembling, maintenance and inspection thereof.
However, an inductance element is backward in miniaturization. In a coil formed by winding a conductor to be packaged as a chip element on a substrate by solder dipping, there remain unsolvable problems with respect to heat resistance of the insulating layer coating the conductor and connection of the conductor with external terminals.
Examples of conventional miniature inductance elements are well known in the art by, for example, "Low Cost, High Frequency Radio Frequency Transformer" disclosed in U.S. Pat. No. 4,134,091 granted to Rogers, "Wire Coil Assembly for an Electrical Circuit" in U.S. Pat. No. 4,229,722 to Olsen, "Miniature High Frequency Coil Assembly or Transformer" in U.S. Pat. No. 4,245,207 to Murakami et al. and Japanese Patent Laying-open Gazette No. 92807/1982.
FIGS. 1 to 3 are sectional views respectively showing conventional miniature inductance elements.
The miniature inductance element as shown in FIG. 1 comprises a magnetic substance such as a drum-shaped core 1 and winding 2 wound around the same. Both ends 3 of the winding 2 are bent along the surfaces of silver electrodes 5 formed on the end surfaces of flange portions 4 on both ends of the core 1, so that the ends 3 of the winding 2, the silver electrodes 5 and lead wires 7 are electrically connected with each other through solder 6.
FIG. 2 shows another conventional miniature inductance element which comprises a drum-shaped core 1 provided in the bottom surface of its flange portion 4 with protruding lead wires 7 and winding 2, both end portions 3 of which are respectively wound around the lead wires 7 to be connected thereto through solder 6.
Both miniature inductance elements as shown in FIGS. 1 and 2 require the lead wires 7 and the solder 6, and cannot be miniaturized like a chip resistor and a chip capacitor.
FIG. 3 shows a chip inductance element which has been proposed by Japanese Patent Laying-open Gazette No. 43513/1984. The miniature inductance element as shown in FIG. 3 comprises a drum-shaped core 1 and winding 2 wound around the same. The core 1 is provided in the bottom surface of its flange portion 4 with silver electrodes 5 at a prescribed interval so that end portions of the winding 2 are bent along the surfaces of the silver electrodes 5 to be connected thereto by solder 6. The chip inductance element as shown in FIG. 3 is fixed to a desired electrode on a circuit substrate through the solder 6 on the silver electrodes 5.
In the aforementioned miniature and chip inductance elements, however, insulating coating material for the winding may have been melted by the heat applied to package the elements on circuit substrates by solder, leading to rare short circuits. In the chip inductance element, further, a great amount of solder, which amount cannot be kept constant, may adhere to the silver electrodes 5, whereby the element might be bonded to the circuit substrate in an inclined state.